Dental matrix retainer claps are used by dentists to permit missing portions of a tooth to be replaced following cavity preparation, so that an amalgam, composite resin, or temporary dressing may be inserted. State of the art dental matrix retainer clamps typically comprise a main body element and a head element pivotally mounted on the main body element. A narrow band of very thin metal is operatively retained by a the retainer clamp so as to exit one end of the head element through a co-operating centrally located slot in the head element. The metal matrix band tends to bias the head element towards a generally medial angular orientation with respect to the holding element due to the springiness of the metal material. The ends of the metal matrix band are retained within the main body element and the remainder of the metal matrix band forms a loop exterior to the retainer clamp. In use, the loop is fitted around a tooth and an adjustment mechanism integral with the main body element allows for adjustment of the size of the loop.
The head element is typically angularly adjustable with respect to the main body element so as to permit the main body element to be positioned away from the tooth being worked on and positioned towards the adjacent teeth. When the metal matrix band is in place around a tooth, retained securely thereat by a dental matrix retainer clamp, it is desirable that the head element be retained as far as possible to one side or the other, at an extreme angular position, in order to keep the holding element from getting in the way of the dentist as he accesses the tooth being worked on. Due to the springiness of the metal matrix band that passes through the head element, it is difficult to keep the head element retained as far as possible to one extreme side or the other of the holding element. Means to properly and adequately retain the head element of a dental matrix retainer clamp in a given position, especially an extreme position, with respect to its holding mechanism, are not known in the prior art.
U.S. Pat. No. 5,055,045, which issued to the present inventors, discloses a dental matrix retainer clamp that has an angularly adjustable head element. The angular position of the head element is maintained by way of a mounting pin on the main body element that frictionally engages the head element. It has been found that this above described arrangement does not provide adequate retention of a set position of the head element with respect to the main body element, as the main body element may be easily moved slightly with respect to the head element. Especially, it does not provide for adequate retention of a set position if the head element is at an extreme angular position, as the metal matrix band tends to bias the head element back towards a central position.
German Patent 26 03 130, published Aug. 4, 1977, discloses a dental matrix retainer clamp wherein there is a hollow tube and a head element that contains a slot that is mounted at the end of the tube. An adjusting knob is provided, and the head element can be rotated so that a band protruding from the head element can be oriented at an angle to the longitudinal axis of the body. Moreover, the present invention is specifically directed to a dental matrix retainer clamp which can be used only once and which must be discarded after use.
It is an object of the present invention to provide a head element for use in conjunction with a dental matrix retainer clamp, wherein the head element is securely retained in at least one set angular position with respect to the holding mechanism of the dental matrix retainer clamp.
It is another object of the present invention to provide a head element for use in conjunction with a dental matrix retainer clamp, wherein the head element is securely retained in an extreme set angular position with respect to the holding mechanism of the dental matrix retainer clamp.
A further problem is encountered with prior art dental matrix retainer clamps when the metal matrix band is tightened in place on a tooth. The head element is not securely positioned in supporting relation against the metal matrix band that is looped around a tooth, even when the head element is at an extreme angular position. The head element does not therefore help support the metal matrix band against the tooth. It is important, or at least desirable, that the head element remain in supporting relation against the metal matrix band looped around a tooth. An adequate and proper anterior surface for the head element, especially one that provides adequate and proper support for the metal matrix band, is not known in the prior art.
It is an object of the present invention to provide a head element that has an adequate and proper anterior surface adapted to securely support the metal matrix band of the dental matrix retainer clamp in substantially unmoving supportive engagement with a tooth.